Poxviruses, and in particular vaccinia virus, have been utilized as systems for the expression of proteins in eukaryotic cells and as a carrier for the presentation of antigens. The capacity to incorporate large amounts of DNA coupled with their wide host range allows for the expression and correct processing of a great variety of proteins in many cell lines. High level expression vectors have been constructed by expressing bacteriophage RNA polymerase genes in vaccinia. These vectors express high levels of any gene located behind the bacteriophage promoter. We have developed a conditionally lethal vaccinia virus which expresses the T7 bacteriophage RNA polymerase. Under the restrictive conditions of elevated temperature the virus undergoes an abortive infection where greatly reduced amounts of the vaccinia late or post-replicative genes are synthesized. We are quantitating the absolute level of expression of foriegn genes in this system and comparing its utility to presently available vaccinia T7 expression systems. The strong humoral and cellular immune response elicited by poxviruses has led to their wide use as delivery vehicles for establishing protective immunity and antigen presentation for immunosurveillance. Poxviruses, and in particular vaccinia virus, have been utilized as systems for the expression of proteins in eukaryotic cells and as a carrier for the presentation of antigens. The capacity to incorporate large amounts of DNA coupled with their wide host range allows for the expression and correct processing of a great variety of proteins in many cell lines. High level expression vectors have been constructed by expressing bacteriophage RNA polymerase genes in vaccinia. These vectors express high levels of any gene located behind the bacteriophage promoter. We have developed a conditionally lethal vaccinia virus which expresses the T7 bacteriophage RNA polymerase. Under the restrictive conditions of elevated temperature the virus undergoes an abortive infection where greatly reduced amounts of the late or post-replicative genes are synthesized. We are quantitating the absolute level of expression of foriegn genes in this system and comparing its utility to presently available vaccinia T7 expression systems. The strong humoral and cellular immune response elicited by poxviruses has led to their wide use as delivery vehicles for establishing protective immunity and antigen presentation for immunosurveillance. This lab is working on poxvirus recombinant technology with the aim of developing a new generation of poxvirus based vectors. Our primary efforts involve the development of direct ligation vectors for more efficient chimera construction and the design of attenuated viruses with host range defects to increase their safety, especially for immunocompromised hosts.